This invention relates to a syringe, comprising a barrel, a pushing rod, and a needle kit, wherein the barrel has an opening at one end for the pushing rod to be airtightly inserted and slide in the barrel, and has an abutting face at the other end the abutting face is protrudingly disposed thereon integrally with an outlet neck and the needle kit is fit to the outer edge of the outlet neck the connecting location of the outlet neck and the abutting face is defined as a connection section which is surroundingly disposed with a combining section at the inner edge, so as to make the thickness of the connection section relatively thinner compared with those of the outlet neck and the abutting face to form a pre-rupture region and the pushing rod is protrudingly disposed with a combination part at the inner end, so as to be rotarily combined and positioned mutually with the combining section at the inner edge of the connection section and to make the pre-rupture region damaged and fractured due to over-tightened and forward torsion and pushing force, making the outlet neck and the barrel separate and enabling the needle kit to be pulled back into the barrel.一種注射器包括有一針筒、一推桿及一針頭套件,其中針筒一端有一開口,俾供推桿氣密地插入而可於針筒內滑動,而針筒另一端具有一頂面,於頂面上一體凸設有一出口頸,而針頭套件套於出口頸之外側緣;出口頸與頂面連接之處界定為一連接段,連接段之內側緣環設有一結合段,藉此令連接段之厚度相較於出口頸及頂面呈相對薄弱以形成預斷區;推桿之內端凸設有一結合部,藉此與連接段內側緣之結合段以旋轉方式相互結合定位,且藉由過度旋緊且前進之扭力及推力令薄弱的預斷區遭到破壞而斷裂,使出口頸與針筒分離,而可將針頭套件拉回針筒內。1...針筒11...容室12...開口13...頂面14...出口頸141...階級槽15...預斷區17...保護牆19...連接段191...內側緣192...斜螺紋段1921...溝槽193...環槽2...推桿21...內端211...止封膠圈22...外端23...結合部231...嵌卡塊232...斜螺牙段24...頂推塊241...頂面25...小徑段3...針頭套件
